NASA tests deployment of Roman Space Telescope ‘visor’

The “visor” for NASA’s Nancy Grace Roman Space Telescope recently completed several environmental tests simulating the conditions it will encounter during launch and in space. Called the Deployable Aperture Cover, the large sunshade is designed to block unwanted light from entering the telescope. This milestone marks the halfway point in the visor’s final testing sprint, bringing it closer to integration with Roman’s other subsystems this fall.

Designed and built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the deployable sunshield consists of two layers of reinforced thermal blankets, distinguishing it from previous rigid sunshields, such as those on NASA’s Hubble Space Telescope. The sunshield will remain folded during launch and deploy once Roman is in space using three arms that lift when triggered electronically.

“With a flexible deployable device like the Deployable Aperture Cover, it’s very difficult to model and predict exactly what it’s going to do. You just have to test it,” said Matthew Neuman, DAC mechanical engineer at Goddard. “Passing these tests now proves that this system works.”

In its first major environmental test, the aperture cover withstood conditions simulating those it will face in space. It was sealed inside NASA’s Goddard Space Environment Simulator, a massive chamber capable of extremely low pressure and a wide temperature range.

Technicians placed the DAC near six radiators (a solar simulator) and thermal simulators representing the outer barrel assembly and solar shield of Roman’s solar array. Since these two components will eventually form a subsystem with the deployable aperture cover, replicating their temperatures allows engineers to understand how heat will actually flow when Roman is in space.

In space, the Deployable Aperture Cover is expected to operate at -67 degrees Fahrenheit, or -55 degrees Celsius. However, recent tests have cooled the cover to -94 degrees Fahrenheit, or -70 degrees Celsius, ensuring it will operate even in unexpectedly cold conditions.

Once cooled, technicians triggered its deployment, monitoring it closely with onboard cameras and sensors. Within about a minute, the sunshield deployed successfully, proving its resilience in extreme space conditions.

“This was probably the environmental test that we were most nervous about,” said Brian Simpson, design lead for the Deployable Aperture Cover project at NASA Goddard. “If there’s a reason the Deployable Aperture Cover is getting stuck or not fully deploying, it’s because the material has become rigid and frozen or stuck to itself.”

If the sunshield were to stall or partially deploy, it would obscure Roman’s view, significantly limiting the mission’s scientific capabilities.

After successfully passing thermal vacuum testing, the deployable sunshield underwent acoustic testing to simulate the intense noise of launch, which can cause vibrations at higher frequencies than the jolts of the launch itself. During this test, the sunshield remained stowed, suspended inside one of Goddard’s acoustic chambers, a large room equipped with two gigantic horns and overhead microphones to monitor sound levels.

With the deployable sunshade equipped with sensors, the noise level of the acoustic test increased, until the sunshade was subjected to a noise of 138 decibels for a full minute, louder than a jet plane taking off at short range! Technicians carefully monitored the sunshade’s response to the powerful acoustics and collected valuable data, concluding that the test was successful.

“We’ve spent the better part of a year building the flight assembly,” Simpson said. “We’re finally getting to the exciting part where we get to test it. We’re confident we’ll do it without a hitch, but after each test we can’t help but breathe a collective sigh of relief.”

Next, the deployable aperture cover will undergo its final two phases of testing. These evaluations will measure the sunshade’s natural frequency and its response to launch vibrations. Then, the deployable aperture cover will be integrated into the entire outer body and the solar array sunshade this fall.